If we're collecting exemplars, I'd like to add Bartosz Ciechanowski's superlative
articles, like the ones on
bicycles and
sound. His articles are the best examples I know of interactive content that complements long-form text content.
The critical issue is security. Security is the reason the graph extension is not enabled. Security is the reason why interactive SVGs are not enabled. Interactive visualizations have a programmatic element that consists of code that executes in the user's browser. Such code needs to be carefully sandboxed to ensure it cannot be used to exfiltrate user data or surreptitiously perform actions on wiki.
I think it's fundamentally a human scaling problem. Being able to create good interactive content is just a much more niche skill than being able to create good text content. Interactive animations were very much part of Yuri's
vision for the Graph extension, but during the decade Graph was deployed in production the number of such animations made was approximately zero. Granted Vega is probably not the easiest framework for creating animations, but I don't think there are other tools which would make it much easier. You could just write arbitrary Javascript and package it as a gadget; but no one did that either. Instead, both gadgets and Graph usage are mostly focused on very basic things like showing a chess board or showing bar charts, because those are the things that can be reused across a large number of articles without manually tailoring the code to each, so the economics of creating them work out.
Security is a challenge but could be worked around via iframes. But it's hard to justify the effort required for doing that when there is no community of animation makers interested in it - there are plenty of volunteers who want to have animations, but it's not very clear that there are any who want to make animations. This is the same problem geni mentioned for videos - a lot of people say "we should have more videos", but it's not very clear who would make them. If platform support were the bottleneck here, I think the platform support would happen. But as things look now, it would just be a poor investment of resources IMO (compared to e.g. the Gadgets extension or Toolforge or Scribunto which do sustain vibrant volunteer ecosystems which are significantly held back by the limitations of these platforms).